Angelica and Alcina are related.
Early on in Innamorato, Angelica can work magic, though this is dropped later on; her father is a sorcerer, who made many of the magical artefacts in the story. This could be explained by fay ancestry. Angelica is also blonde, despite being Chinese; Alcina is blonde (though this is a glamour). Although they are both described as being very beautiful, they seem to have a rather more powerful effect on men than just this. Since Alcina is apparently hundreds of years old, she could easily be Angelica's grandmother, or even further back in the family tree. It's entirely possible she at one point hooked up with an Emperor of Cathay and had a baby before getting bored of him. (This would also make Ruggiero's behaviour towards Angelica slightly less What the Hell, Hero? as at the point he meets her he is still recovering from a spell that made him fall in love with Alcina, and it could be affecting his behaviour).To add to the family tree: out of the three fairy gardens featuring in Innamorato, Alcina's sister sister Morgana is the only one whose garden Angelica is not directly responsible for the destruction of. Alcina and Morgana are described as being the daughters of Love: while this sounds metaphorical, Love actually appeared at the end of Innamorato, beat Rinaldo up, and made him fall in love with Angelica (who was still pining after him at this point). Looking out for his descendent? When Angelica and Medor get married, Love is described as being at the wedding. While this is probably a metaphor, it's possible a fairy relative has actually shown up.
Brandimart is an albino
Despite being Japanese, Brandimart and his brother Ziliante are blonde. This also doesn't seem to be normal: Manodante doesn't seem to recognise Brandimart as being from the Far Isles, since he mistakes him for Orlando. Brnadimart's mother is named Albina, and albinism is to some extent genetic. Marfisa and Fiordelisa go way back
When Marfisa first appears, it's Fiordelisa who recognises her, explains to Rinaldo who she is, and warns him to stay the hell away from her. Later, Marfisa runs into Fiordelisa and decides to throw her off a cliff. Marfisa is pretty Ax-Crazy and has just been chasing a horse for what appears to be weeks without food, water or rest so is probably not in the best of moods, and uses this to steal Brandimart's horse and armour, it could be that she knows Fiordelisa, and doesn't like her.Since they're both revealed to have been sold into slavery as children, they could have been sold at the same time, by the same people, and know each other from then. Fiordelisa did something to piss Little Marfisa off, and learnt to be scared of her.